Sludge is tested and managed in accordance with the ZDHC Wastewater and Sludge Guidelines
This is the new version of Wastewater & Sludge Guidelines
This version (V2) is published and available to prepare for. It will replace the active version (V1) and take effect from 01 Nov 2026. Until then, continue using Wastewater & Sludge Guidelines V1. View Changelog
Wastewater treatment systems consist of many different processes resulting in many kinds of sludge. These in scope and out of scope tables provides a comprehensive list and characteristics of different types of sludges, defining which are in-scope or out of scope for the applicability of the Wastewater and Sludge Guidelines.
It is important that suppliers maintain records on the testing and disposal of sludge to ensure that they can demonstrate their chosen disposal pathway and that the sludge is conformant for that pathway.
Supplier required actions
- The suppliers should identify their sludge disposal pathway.
- For the supplier’s chosen disposal pathway, complete information and records of the pathway should be maintained, including the sludge manifest required for legal purposes.
- Where sludge is disposed of through authorised third-party waste contractors, suppliers should make an effort to gather all relevant information on the disposal pathway from the waste contractor.
- ZDHC sludge disposal pathway templates can be used by the supplier to input the information relevant to their major disposal pathway.
- A supplier should maintain a signed declaration template (with complete information about the disposal pathway) and provide it to the sampler from the ZDHC Approved Wastewater and Sludge Laboratory during the visit to collect wastewater and sludge samples for testing. This will help the laboratory to determine the applicable testing and reporting requirements for the sludge sample.
Download sludge disposal pathway declaration template
ZDHC sludge disposal pathways
There are seven disposal pathways.
If the pathway is unknown the facility should assume Disposal Pathway F.
- Pathway A – On-site or off-site incineration at >1000℃
- Pathway B - Landfill with significant control measures
- Disposal Pathway C - Building products processed at >1000℃
- Disposal Pathway D - Landfill with limited control measures
- Disposal Pathway E - Off-site incineration and building products processed at <1000℃
- Disposal Pathway F - Landfills with no control measures
- Disposal Pathway G - Land application for a specific purpose in approved areas
Sample and test sludge
Sludge sampling and testing requirements depend on the disposal pathway.
The purpose of sampling and testing of sludge is:
- To check for the detection of ZDHC MRSL substances as an indicator of deliberate use in input chemical formulations.
- To confirm that requirements for the major disposal pathway are met through the detection of metals and other applicable conventional parameters.
Testing requirements for sludge
Disposal pathway A testing requirements
- Test ZDHC MRSL substances
- Test % solids
Disposal pathway B testing requirements
- Test ZDHC MRSL substances
- Test % solids
Disposal pathway C testing requirements
- Test ZDHC MRSL substances
- Test % solids
Disposal pathway D testing requirements
- Test ZDHC MRSL substances.
- Test listed metals to check if they exceed the threshold limit values. If a listed metal(s) exceeds the threshold value, test metal leachate(s).
- Test for conventional parameters (pH, % solids and paint filter test) and cyanide as applicable.
Disposal pathway E testing requirements
- Test ZDHC MRSL substances.
- Test listed metals to check if they exceed the threshold limit values. If a listed metal(s) exceeds the threshold value, test metal leachate(s).
- Test for conventional parameters (pH, faecal coliform, % solids and paint filter test) and cyanide as applicable.
Disposal pathway F testing requirements
- Test ZDHC MRSL substances.
- Test listed metals to check if they exceed the threshold limit values. If a listed metal(s) exceeds the threshold value, test metal leachate(s).
- Test for conventional parameters (pH, faecal coliform, % solids and paint filter test) and cyanide as applicable.
Disposal pathway G testing requirements
- Test ZDHC MRSL substances.
- Test listed metals to check if they exceed the threshold limit values. If a listed metal(s) exceeds the threshold value, test metal leachate(s).
- Test for conventional parameters (pH, faecal coliform, % solids and paint filter test) and cyanide as applicable.